With rapid advance in automation industry, demands of high-reliability and high-performance upon the control instruments are significantly rising. Various sensors are widely used for the purpose of automatic and persistent monitoring. In particular, the current sensor plays one of crucial roles for the panel detection and control in both the industrial and the domestic applications.
Currently, the current sensors in the art can be theoretically classified into four categories: 1. the shunt resistor according to the Ohm's law, 2. the current transformer according to the Faraday's law of induction 3. The Hall element according to the magnetic detection, and 4. the fiber optic current sensor according to the Faraday effect. The former two types are criticized for their mass heat generation due to direct measuring and for irrelevance to the multi-core power cable due to their cumbersome volumes. On the other hand, the Hall element that is tiny in volume and can function without direct contacting would be superior to the former two types of the current sensors. However, before adopting the Hall elements to the multi-core power cables, the distance between the Hall element and the power cable to be detected is critical. In addition, the fiber optic current sensor is low in sensitivity, difficult in maintenance, and complicated in structuring, and thus its application is pretty limited.
According to the Amp principle, when an electric current flows through a conductive object, a surrounding magnetic field would be induced. The magnitude of the induced magnetic field is proportional to the current in the conductive object, but is inversely proportional to the spacing in between. Through the knowledge of the induced magnetic field, the current through the conductive object can be realized. However, all the aforesaid or not said non-contact current sensors in the art have a common shortcoming of measurement bias due to inappropriate mounting positions. Therefore, it is definite that an improvement upon the non-contact current sensors for compensating the position-induced measurement bias is urgent and welcome to the skill in the art.